Method for determining imbalance in drum washing machine

ABSTRACT

A method for determining an imbalance in a drum washing machine includes increasing a rotational speed of a motor of the drum washing machine to a target RPM, and then measuring an RPM for each rotation section; comparing the RPM for each rotation section to an RPM limit to obtain a comparison result; and determining whether an imbalance occurs according to the comparison result.

TECHNICAL FIELD

The present invention relates to a drum washing machine, and more particularly, to an imbalance determination method for a drum washing machine, which determines whether an imbalance occurs or not using a rotational speed (e.g., RPM) for each rotation section and an RPM variation during a spin-drying process.

BACKGROUND ART

In general, washing machines may be classified as a pulsator washing machine and a drum washing machine.

The pulsator washing machine is a water tank-type washing machine which rotates a washing tub on a vertical axis, and rotates a pulsator to agitate and wash laundry items dipped or at least partially immersed in wash water of the washing tub.

The drum washing machine washes laundry items using a force that is caused when the laundry items fall downward after a horizontal drum housing the laundry items therein is rotated to move the laundry items upward, and a frictional force between the rotating drum and the laundry items is imparted to the laundry items.

In particular, when the drum washing machine is used, damage to laundry items may be reduced, the laundry items may not get tangled, and a washing effect of beating and rubbing the laundry items may be achieved. Recently, the drum washing machine is frequently used.

The above-described configuration is background for helping an understanding of the present invention, and does not necessarily mean that it is widely known in the technical field to which the present invention pertains.

DISCLOSURE Technical Problem

Conventional drum washing machines perform a balance spin-drying process such that laundry items adhere on an inner wall of the drum before the main spin-drying process is performed.

During the balance spin-drying process, whether an imbalance occurs or not is determined. When a balancer attached to the tub has a small weight, the tub supporting the drum is moved according to the rotation of the drum.

However, since the occurrence of the imbalance is determined based on only a variation in RPM for each rotation section, the increase and decrease in RPM caused by motion of the tub may not be sufficiently reflected. Thus, the imbalance determination may be erroneous or not performed in a normal manner.

The present invention can solve such problems, and an aspect of the invention is to provide a method for determining an imbalance in a drum washing machine, which additionally determines a rotational speed (e.g., an RPM) for each rotation section, as well as a variation of an RPM for each rotation section, and determines whether or not an imbalance occurs during the spin-drying process.

Technical Solution

According to an aspect of the invention, a method for determining an imbalance in a drum washing machine includes: increasing an RPM of a motor to a target RPM, and then measuring a rotational speed (e.g., an RPM) for each rotation section; comparing the rotational speed (e.g., RPM) for each rotation section to an RPM limit to obtain a comparison result; and determining whether or not an imbalance occurs, according to the comparison result.

Determining whether or not the imbalance occurs may include determining that the imbalance occurs when the RPM for each rotation section deviates from the RPM limit.

Determining whether or not the imbalance occurs may further include determining a variation of the RPM for each rotation section when the RPM for each rotation section falls within the RPM limit.

When the variation of the RPM for each rotation section falls within a preset value, it may be determined that the imbalance does not occur.

When the variation of the RPM for each rotation section exceeds a preset value, it may be determined that the imbalance occurred.

Advantageous Effects

According to one or more embodiments of the invention, both the rotational speed (e.g., RPM) for each rotation section and the variation of the RPM for each rotation section are determined to improve the precision of the imbalance determination.

DESCRIPTION OF DRAWINGS

The above and other aspects, features and advantages of the invention will become apparent from the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a block configuration diagram of a device for determining an imbalance of a drum washing machine in accordance with one or more embodiments of the present invention;

FIG. 2 is a flowchart for explaining an imbalance determination method for a drum washing machine in accordance with embodiment(s) of the present invention;

FIG. 3 is a graph illustrating the RPM of a motor during a balance spin-drying process in accordance with embodiment(s) of the present invention; and

FIG. 4 is a diagram illustrating rotation sections of a drum in accordance with embodiment(s) of the present invention.

DETAILED DESCRIPTION

Embodiments of the invention will hereinafter be described in detail with reference to the accompanying drawings. It should be noted that the drawings may not be to precise scale and may be exaggerated in thickness of lines or sizes of components for descriptive convenience and clarity only. Furthermore, the terms as used herein are defined by taking functions of the invention into account and can be changed according to the custom or intention of users or operators. Therefore, definition of the terms should be made according to the overall disclosures set forth herein.

FIG. 1 is a block configuration diagram of an imbalance determination device of a drum washing machine in accordance with one or more embodiments of the present invention.

Referring to FIG. 1, the imbalance determination device in accordance with one or more embodiments of the present invention includes a control unit 10, a motor 20, and a load measurement unit 30.

The motor 20 serves to rotate a drum of the washing machine (not illustrated). The motor 20 may include a universal motor, for example, configured to rotate the drum.

The motor 20 may be directly installed on the center axis of the drum (e.g., a direct-drive motor that directly drives an axle to which the drum is fixed or attached) or installed at one side of the tub (e.g., a belt-drive motor that drives a belt that, in turn, drives a wheel and/or axle to which the drum is fixed or attached). When the motor 20 is installed at one side of the tub, torque generated by the motor 20 is transmitted through a power transmission device (not illustrated), for example, a belt, a belt pulley or gear.

The load measurement unit 30 serves to measure the load of the motor 20, which is caused by rotations of the drum.

When a spin-drying process is started, the control unit 10 performs a balance spin-drying process and a main spin-drying process while controlling the motor 20.

The main spin-drying process refers to a process of rotating the drum at high speed so as to remove wash water soaking into laundry items.

The balance spin-drying process refers to a process of measuring an imbalance value to determine whether or not an imbalance occurs, while laundry items adhere on the inner wall of the drum (as a result of rotational force) before the main spin-drying process is performed.

The balance spin-drying process includes an agitation operation, a laundry adherence operation, a water removal operation, and an imbalance determination operation. The agitation operation agitates laundry items within the drum so that the laundry items are not concentrated onto one side of the drum. The laundry adherence operation determines whether or not an imbalance occurs when the laundry items adhere to the inner wall of the drum (e.g., during relatively low-speed rotation of the drum). The water removal operation removes wash water and/or foam from the laundry items. The imbalance determination operation determines whether or not an imbalance occurs after the water removal operation.

In particular, during the laundry adherence operation and the imbalance determination operation, the motor 20 is rotated at a target rotation speed so that the laundry items adhere on the inner wall of the drum. Then, the RPM of the motor 20 is measured on the basis of the load of the motor 20 as measured by the load measurement unit 30, and whether an imbalance occurs is determined on the basis of the RPM of the motor 20.

The control unit 10 measures the RPM of the motor 20 for a plurality of rotation sections of the drum (e.g., each rotation section). The control unit 10 determines whether or not the RPM measured for each of the plurality of rotation sections falls within a RPM limit. When the RPM deviates from the RPM limit, the control unit 10 determines that an imbalance occurs.

In the conventional method, a variation of the RPM measured for each rotation section of the drum is compared to a preset value so as to determine whether or not an imbalance occurs. However, according to embodiment(s) of the present invention, when the variation of the RPM for each rotation section falls within the preset value, the RPM for each rotation section can be used in addition to the variation of the RPM for each rotation section to determine whether or not an imbalance occurs. Thus, it is possible to improve the precision and/or accuracy of the imbalance determination.

On the other hand, when the RPM measured for each of the plurality of rotation sections falls within the RPM limit, a variation of the RPM for each rotation section may be extracted, and whether or not the variation is within the preset value may be determined. Then, whether an imbalance occurs or not is determined according to the determination result.

The RPM limit may be within 10% of the target RPM.

Referring to FIGS. 2, 3 and 4, a method for determining an imbalance in a drum washing machine in accordance with embodiment(s) of the present invention will be described in detail.

FIG. 2 is a flowchart for explaining the method for determining an imbalance in a drum washing machine in accordance with embodiment(s) of the present invention. FIG. 3 is a graph illustrating the rotational speed of the motor (in RPM) during a balance spin-drying process in accordance with embodiment(s) of the present invention. FIG. 4 is a diagram illustrating rotation sections of the drum in accordance with an embodiment of the present invention.

Referring to FIG. 2, the control unit 10 controls the motor 20 to increase the RPM of the motor 20 to 45 RPM, thereby agitating the drum in the side-to-side direction, at step S10. Thus, laundry items within the drum are uniformly spread so as not to be concentrated on one side of the Wb. However, during the agitation operation, the motor may rotate the drum at a speed of from 25 to 75 RPM.

Then, the control unit 10 increases the RPM of the motor 20 to the target RPM and checks whether or not the RPM of the motor 20 reaches the target RPM, at steps S20 and S30.

The target RPM may be a value of from 50 to 150 RPM (e.g., 95 RPM). The target RPM is not limited to 95 RPM, but may be set to a speed at which the laundry items adhere on the inner wall of the drum.

When the RPM of the motor 20 reaches the target RPM, the control unit 10 does not control the motor 20. The motor 20 and drum are allowed to freely rotate (e.g., by inertia). At this time, the load measurement unit 30 measures the load of the motor 20 for each of a plurality of rotation sections of the motor 20, and the control unit 10 measures an RPM (e.g., of the drum) for each rotation section based on the load of the motor 20, at step S40. In various embodiments, the number of rotation sections is 2×M or 4×N, where M is an integer of from 1 to 12 (e.g., from 3 to 8), and M is an integer of from 1 to 6 (e.g., from 2 to 4).

Referring to FIG. 4, the rotation of the motor 20 (or the rotation of the drum corresponding to the rotational drive of the motor 20) is divided into a plurality of rotation sections depending on the rotation angle of the motor 20, and the RPM of the motor 20 is measured for each rotation section.

In one embodiment, the motor 20 includes 12 rotation sections A to L, obtained by dividing the rotational cycle of the motor 20 by 30 degrees.

In this way, the RPM for each rotation section may be measured and compared to the RPM limit so as to determine whether or not the RPM for each rotation section falls within the RPM limit, at step S50.

When the RPM for each rotation section deviates from the RPM limit, the control unit 10 determines that an imbalance occurs, at step S90.

As such, the control unit 10 may check whether or not the RPM for each rotation section falls within the RPM limit, and reflect an error caused by motion of the tub, thereby improving the precision and/or accuracy of the imbalance determination.

When the RPM for each rotation section falls within the RPM limit, a variation of the RPM for each rotation section is extracted at step S60.

The variation of the RPM for each rotation section is a difference in RPM between the respective rotation sections. For example, the variation may include a difference in RPM between the rotation sections A and B or a difference in RPM between the rotation sections B and C as illustrated in FIG. 4.

When the variation of the RPM for each rotation section is extracted, whether the variation of the RPM for each of the plurality of rotation sections falls within a preset value is determined at step S70. The preset value is a reference value for determining whether an imbalance occurs. When the variation of the RPM for each rotation section deviates from the preset value, it may indicate that an RPM in a next rotation section is significantly different in comparison to an RPM in a current rotation section. In this case, the control unit 10 may determine that an imbalance occurs. Alternatively or additionally, the variation across all of the plurality of rotation sections may be determined and compared to a preset value, and if the variation of the RPM across all rotation sections deviates from the preset value, it may indicate that an RPM in one rotation section is significantly different in comparison to an RPM in another rotation section.

Thus, when the variation of the RPM for each rotation section falls within the preset value, the control unit 10 determines that an imbalance does not occur at step S80, and when the variation of the RPM for each rotation section exceeds the preset value, the control unit 10 determines that an imbalance occurs at step S90.

When it is determined that an imbalance does not occur, the control unit 10 increases the RPM of the motor 20 to perform the water removal operation, and when it is determined that an imbalance occurs, the control unit 10 performs the balance spin-drying process again. The preset or target RPM for the water removal operation is higher than the target RPM for the imbalance determination, and may be a value of from 125 to 250 RPM (e.g., 180 RPM), and the preset or target RPM for the second imbalance determination may be the same as the first imbalance determination (e.g., during the laundry adherence operation). The preset or target RPM for the main spin-drying process is higher than the preset or target RPM for the imbalance determination(s) and the water removal operation, and may be a value of from 200 to 400 RPM (e.g., 300 RPM), but is not limited to this value or range. Rather, it may be set to a speed at which free water is substantially removed from the laundry items.

Although some embodiments have been provided to illustrate the invention in conjunction with the drawings, it will be apparent to those skilled in the art that the embodiments are given by way of illustration only, and that various modifications and equivalent embodiments can be made without departing from the spirit and scope of the invention. The scope of the invention should be limited only by the accompanying claims. 

1. A method for determining an imbalance in a drum washing machine, comprising: increasing a rotational speed of a motor of the drum washing machine to a target RPM, and then measuring an RPM for each rotation section of the motor; comparing the RPM for each rotation section to an RPM limit to obtain a comparison result; and determining whether an imbalance occurs according to the comparison result.
 2. The method of claim 1, wherein determining whether the imbalance occurs comprises determining that the imbalance occurs when the RPM for each rotation section deviates from the RPM limit.
 3. The method of claim 1, wherein determining whether the imbalance occurs further comprises determining a variation of the RPM for each rotation section when the RPM for each rotation section falls within the RPM limit.
 4. The method of claim 3, wherein when the variation of the RPM for each rotation section falls within a preset value, the imbalance does not occur.
 5. The method of claim 3, wherein when the variation of the RPM for each rotation section exceeds a preset value, the imbalance occurs.
 6. The method of claim 1, wherein the drum washing machine further comprises a control unit, a drum rotated by the motor, and a load measurement unit.
 7. The method of claim 6, wherein the control unit controls the motor and measures the rotational speed of the motor.
 8. The method of claim 1, wherein the load measurement unit measures a load of the motor caused by rotational movement of the drum.
 9. The method of claim 1, wherein the target RPM is a value of from 50 to 150 RPM.
 10. The method of claim 1, further comprising: allowing the motor and drum to freely rotate when the motor reaches the target RPM, measuring a load of the motor for each of a plurality of rotation sections of the motor, and measuring a rotational speed for each of the plurality of rotation sections based on the load of the motor.
 11. A method of spin-drying laundry in a drum washing machine, comprising: balance spin-drying the laundry by a process comprising: determining an imbalance in the drum washing machine according to the method of claim 1, and removing wash water and/or foam from the laundry when no imbalance occurs; and main spin-drying the laundry at a rotational speed higher than the target RPM.
 12. The method of claim 11, further comprising determining the imbalance when the laundry adheres to an inner wall of a drum rotated by the motor.
 13. The method of claim 12, wherein the target RPM is a value of from 50 to 150 RPM.
 14. The method of claim 11, further comprising agitating the laundry at a rotational speed less than the target RPM so that the laundry items do not concentrate onto one side of a drum rotated by the motor.
 15. The method of claim 11, further comprising, after removing wash water and/or foam from the laundry, determining again whether an imbalance occurs in the drum washing machine.
 16. The method of claim 15, wherein determining again whether an imbalance occurs in the drum washing machine comprises: changing the rotational speed of the motor to the target RPM, and then measuring a second RPM for each rotation section of the motor; comparing the second RPM for each rotation section to the RPM limit to obtain a second comparison result; and determining whether the imbalance occurs according to the second comparison result.
 17. The method of claim 15, wherein wash water and/or foam is removed from the laundry at a rotational speed higher than the target RPM.
 18. The method of claim 17, wherein wash water and/or foam is removed from the laundry at a rotational speed of from 125 to 250 RPM.
 19. The method of claim 11, wherein main spin-drying the laundry is performed at 200 to 400 RPM. 